Charging electronic tubes with mercury



May 1957 D. v. KELLER, JR., ETAL 3,318,649

CHARGING ELECTRONIC TUBES WITH MERCURY Filed 000. 11, 1963 FIG. I

INVENTORS. DOUGLAS V. K FREDERIC E SCOTT THEIR ATTORNEY.

ELUER, JR.

United States Patent 3,318,649 CHARGING ELECTRONIC TUBES WITH MERCURY Douglas V. Keller, In, La Fayette, and Frederick P. Scott, Garden City Park, N .Y., assignors to King Laboratories Inc., Syracuse, N.Y., a corporation of New York Filed Uct. 11, 1963, Ser. No. 316,206 4 Claims. (Ci. 3163) This invention has as an object a mercury containing composition of solid form which can be conveniently handled, and the mercury liberated therefrom by the application of heat.

The invention has as a further object charging electronic tubes with a predetermined amount of mercury Without handling the mercury in the liquid form.

In describing our invention, reference is made to the accompanying drawing in which FIGURE 1 is a side elevational view of an electronic tube containing a mercury alloy support; and

FIGURE 2 is a sectional view of the support taken on line 2-2, FIGURE 1.

In general, the invention consists of a mercury containing alloy which, when heated within a permissible temperature range, such as 400 to 800 C., the mercury is liberated from the alloy. A predetermined quantity of this alloy is inserted in the electronic tube. The envelope of the tube is sealed to the base, and the tube evacuated. The temperature of the alloy is then raised for the liberation of the mercury from the alloy. The required amount of mercury can be obtained readily by controlling the weight of the alloy of controlled mercury content.

The alloy is formed from mercury and a metal selected from Groups IA, IIA or III, including the lanthanides and actinides, of the periodic table, which metal, for convenience, we refer to as a base metal. In theory, all the metals in these groups would serve as the base metal. In making up the alloy however, practical consideration should be kept in mind in the selection of the base metal, such, for example, as availability, cost, chemical activity, radioactivity, conditions under which the alloy will be handled, etc. Magnesium serves excellently as the base metal inasmuch as the resulting alloy is stable at ordinary atmospheric conditions. It forms stable intermetallic phases with the mercury which permits a relatively high percent of mercury in the alloy. Of these metals, those having a greater chemical activity than magnesium result in the alloy having to be shipped in special containers and handled under special conditions. The alloy has a melting point within a good practical range. It is stable at ordinary ambient temperature and at a high relative humidity.

The alloy is formed by melting together the selected base metal and mercury. The solidified alloy is ground up in the form of relatively fine powder. The alloy may be conveniently packaged, shipped and stored for the subsequent liberation of mercury therefrom by the application of heat.

In the process of charging electronic tubes with mercury, a quantity of the alloy is aflixed to a suitable support which is mounted in the tube. After the envelope of the tube is sealed to the base and the tube is evacuated, the alloy is raised to a temperature sufiicient to liberate the mercury. The heating of the alloy can be readily accomplished either by electric resistance, or by radio frequency induction methods, as presently used to flash tube getters.

In the drawings, designates the envelope of an electronic tube sealed to the base 11. A support carrying a quantity of alloy is mounted on the top plate 12 of the electrode supporting structure. The support may vary in form and structure. The form shown consists of a plate 13 formed of thin sheet metal to which a stem 14 is fixed and which, in turn, is fixed to the plate 12 of the tube. The plate 13 is formed with a recess or depression 15 in which a quantity of the alloy is embedded, as shown at 16, FIGURE 2. The plate 13 is formed with a tab portion 17 folded back over the alloy in the recess 15. When the support is heated to a temperature be tween 400-800 C., the mercury will be liberated from the alloy, passing out from under the tab 1'7.

The magnesium mercury alloy may be formed with the following range of percentages by weight: magnesium 30 to 5; mercury 70 to 95.

To further stabilize the above alloy in certain applications, a quantity of transition metal from Group VIII, or mixtures thereof, may be added. For example, an alloy containing magnesium, mercury and nickel, may be formed with the following percentages by weight: mercury 15-95; magnesium 5-65; nickel 10-55.

The addition of nickel to the alloy may prevent oxidation of the base metal, such as the magnesium, or it may serve to raise the temperature at which the alloy will liberate the mercury. In any event, we have found that the addition of nickel to the alloy is effective to prevent any premature liberation of the mercury during the sealing off of the tube.

It will be apparent, the required amount of mercury for release in the tube can be obtained readily by controlling the weight of alloy of controlled mercury content. This method avoids the handling of liquid mercury. The high mercury content alloy may otherwise conveniently serve for the handling, or shipping, of mercury for other purposes.

What we claim is:

1. The method of charging an electronic tube with mercury, the method consisting in preparing an alloy composed of mercury and a metal selected cfrom Groups IA, IIA and III of the periodic table, inserting a quantity of said alloy in the tube, sealing the tube and heating the alloy to a temperature sufficient to liberate the mercury.

2. The method of charging an electronic tube with mercury, the method consisting in preparing an alloy composed of mercury and magnesium, inserting a predetermined quantity of the alloy in the tube, sealing the tube, and then heating the alloy to a temperature suflicient to liberate the mercury.

3. The method of charging an electronic tube with mercury, the method consisting in preparing an alloy composed of mercury, a metal selected from Groups IA, IIA and III, of the periodic table, and one or more metals of Group VIII, placing a quantity of the alloy in the tube, sealing the tube and subjecting the alloy in the tube to a temperature suflicient to liberate the mercury.

4. The method of charging an electronic tube with mercury, the method consisting of preparing an alloy composed of magnesium, mercury and nickel in proportion by weight bf from 15% to mercury; 5% to 65% of magnesium; 10% to 55% of nickel, inserting a quantity of said alloy in a tube and sealing the tube, and subsequently heating the alloy in the tube to a temperature sufficient to liberate the mercury.

Hansen: Constitution of Binary Alloys, 2nd edition, published by McGraw-Hill Book 00., pp. 822, 823 and 824.

FRANK E. BAILEY, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,318,649 May 9, 1967 Douglas V. Keller, Jr., et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, before line 9, insert the following:

This invention has to do with the handling and liberating of mercury, and in particular with charging electronic tubes with mercury. There are several types of electronic tubes that require a proper amount of mercury within the tube in order to function, such for example as thyatron, fluorescent, read-out, mercury vapor, rectifiers, etc.

At the present time, the conventional method of introducing the required quantity of mercury into the tube is accomplished by metering the mercury in liquid form into the tube prior to sealing off the envelope of the tube to the base. In some instances, the equantity of liquid mercury is placed in a capsule, which is inserted into the tube, and the mercury is liberated by heating the capsule sufficiently to evaporate the mercury therefrom. In both cases, it is necessary to handle liquid mercury with all its attending problems, such as spillage and breakage, and these methods are particularly objectionable due to the fact that the mercury vapor is highly toxic with cumulative effects.

Signed and sealed this 21st day of November 1967.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. EDWARD J BRENNER Attesting Officer Commissioner of Patent: 

1. THE METHOD OF CHARGING AN ELECTRONIC TUBE WITH MERCURY, THE METHOD CONSISTING IN PREPARING AN ALLOY COMPOSED OF MERCURY AND A METAL SELECTED FROM GROUPS IA, IIA AND III OF THE PERIODIC TABLE, INSERTING A QUANTITY OF SAID ALLOY IN THE TUBE, SEALING THE TUBE AND HEATING THE ALLOY TO A TEMPERATURE SUFFICIENT TO LIBERATE THE MERCURY. 